mysql - Mysql使用交叉引用选择行但在条件上省略

Question

鉴于这些表：

+---------------+---------+
| Field         | Type    |
+---------------+---------+
| group_id      | int(10) |
| subscriber_id | int(10) |
+---------------+---------+

+---------------+--------------+
| Field         | Type         |
+---------------+--------------+
| subscriber_id | int(10)      |
| firstname     | varchar(50)  |
| lastname      | varchar(50)  |
| company       | varchar(120) |
| position      | varchar(50)  |
| email         | text         |
| lettertype    | varchar(5)   |
| status        | varchar(20)  |
+---------------+--------------+

我使用以下查询来获取订阅者的子集：

SELECT * 
FROM newsletter_subscribe AS a, newsletter_subscriber AS b
WHERE (a.group_id = 1 or a.group_id = 4)AND (a.subscriber_id = b.subscriber_id)

如果在 newsletter_subscribe 中存在 group_id = 3 的行，那么我想做的是从子集中排除，那么该行中的 newsletter_subscribe 将从结果中排除。

我的想法是制作一个临时表来替换a，但我不确定如何去做。

Answer 1

就目前而言，您永远不会得到 group_id=3，因为您只允许组1和4where 子句的第一个术语。如果您想要除 3 之外的所有组，请使用

WHERE (a.group_id <> 3) AND (a.subscriber_id = b.subscriber_id)

也许

WHERE 3 NOT IN (a.group_id, b.group_id) AND (a.subscriber_id = b.subscriber_id)

从两个表中排除它。

Answer 2

SELECT * 
FROM newsletter_subscribe AS a, newsletter_subscriber AS b
WHERE (a.group_id = 1 or a.group_id = 4) AND (a.subscriber_id = b.subscriber_id) AND (b.subscriber_id NOT IN (SELECT subscriber_id FROM newsletter_subscribe WHERE group_id = 3))